Below are list of changes from 2.7b and 2.8, from the Revision History section of the spec.

[The Mantis Number is the entry in the bug database which has all the details on the change, only UEFI Forum members have access to that data, all that is shown in the public spec is the Mantis Number and Bug Title. Non-members will need to use this Description String to try and find the updated section in the spec and look for recent Tianocore implmentation code checkins, or maybe wait for Nikolaj to issue a series of Tweets…]